Stepped Dam Structure for Void-Free Semiconductor Underfill
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Solution Overview
Problem
The occurrence of voids in the underfill material between a semiconductor chip and a mounting substrate deteriorates the reliability of semiconductor packages, as existing underfill processes struggle to effectively manage stress and environmental protection due to differences in thermal expansion coefficients.
Innovation Solution
A semiconductor package design incorporating a dam structure with a lower portion contacting the passivation layer and an upper surface featuring segments of different vertical levels, which controls the underfill material flow and prevents overflow, ensuring the underfill material fills the gap between the chip and substrate without forming voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional underfill process is used to fill the gap between semiconductor chip and substrate, then the gap can be filled with underfill material, but voids form in the underfill material deteriorating reliability
Solution Approach 1:
The dam structure is divided into multiple segments at its upper surface, creating a stepped configuration with different vertical levels. This segmentation allows the underfill material to flow through the gaps between segments, ensuring complete filling and preventing void formation while maintaining structural integrity
Solution Approach 2:
The dam structure transitions from a simple planar barrier to a three-dimensional stepped structure with varying vertical levels. This dimensional change creates flow pathways for the underfill material, enabling it to penetrate and fill the gap completely between the semiconductor chip and substrate
2Manufacturing precision
If the dam structure uses a single vertical level, then the structure is simple, but the underfill material cannot flow properly and voids occur
Solution Approach 1:
The dam structure is divided into multiple segments at its upper surface, creating a stepped configuration with different vertical levels. This segmentation allows the underfill material to flow through the gaps between segments, ensuring complete filling and preventing void formation while maintaining structural integrity
Solution Approach 2:
Different segments of the dam structure have different vertical levels, creating localized variations in height. This local quality differentiation enables the underfill material to flow through specific gaps between segments, ensuring proper filling without requiring complete structural complexity throughout
3Strength
If the underfill material is allowed to overflow freely, then the filling process is simple, but the bonding force between materials deteriorates
Solution Approach 1:
The dam structure with its stepped configuration is prepared in advance to control the underfill material flow paths. This preliminary structural arrangement prevents overflow before it occurs, ensuring proper bonding strength without requiring complex real-time process control
Data Source
AI summary
The inventive concept provides a semiconductor package including a substrate including a passivation layer, a semiconductor chip mounted on the substrate, an underfill material layer between the semiconductor chip and the substrate, and a dam structure on the substrate and surrounding the semiconductor chip, wherein a lower portion of the dam structure is in contact with the passivation layer and is formed of a material that is the same as a material forming the passivation layer, and an upper surface of the dam structure includes a first segment at a first vertical level and a second segment at a second vertical level, wherein the second vertical level is different from the first vertical level.